In launching a new school literacy program the Prime Minister, Julia Gillard, appears to have committed a statistical howler.

Declaring that about 75,000 students failed to meet national minimum standards in the NAPLAN test last year she said, ''without improvement that number could climb to more than 150,000 by 2025''.

The doubling is the result of extrapolating forward the change over one year for 13 years.

"It's good practice to use all of the comparable data not just one change" ... Chris Richardson. Photo: Glenn Hunt

Responding to Fairfax Media's questions on Sunday, the Education Minister's office said: ''The calculation is a Commonwealth analysis based on year 3 NAPLAN data and assumes the change seen between 2011 and 2012 continues out to 2025.''

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But extending forward only the most recent change in a statistic is widely regarded as bad practice, likely to produce nonsense.

''One change does not a trend make,'' the Deloitte Access director Chris Richardson, a former Treasury economist, said.

If, for example, the Commonwealth had extended forward only the most recent change in employment, between December and January, it would have looked as if employment was on track to climb 124,800 in the coming year. But if it had extended forward the previous change, between November and December, employment would have looked on track to slide 45,600.

''It's good practice to use all of the comparable data, not just one change,'' Mr Richardson said. ''The trend is your friend. To construct it, you should use all the comparable data.''

NAPLAN data from 2008 shows reading, spelling and grammar on an improving trend. The proportion of year 3 students failing to meet minimum reading standards fell from 7.9 per cent to 6.5 per cent. The proportion failing to meet minimum spelling standards fell from 7.5 per cent to 6 per cent.

''We will make this reading blitz one of the aims of our school funding reforms,'' Ms Gillard told parents and children at the launch. ''We want to make sure that every child is assessed, every child's strengths and weaknesses on reading are known and every child gets the opportunity to become a great reader.''

The government will ask all schools to sign up to an intensive four-year program in which teachers from kindergarten to year 3 maintain a running record of each student's progress and set out a reading plan that includes the sounding out of words as one of the teaching methods.

No specific funding is allocated for the program, which will be ''embedded in the work we are already doing for school funding reform''.

State education ministers welcomed the program, saying it was similar to their own work.

''Our Early Action for Success strategy will see an additional 900 teachers employed across all school sectors,'' the NSW minister, Adrian Piccoli, said. ''The first 50 literacy and numeracy specialists have already been placed.''

''Obviously any new idea will need to be consistent with Victoria's nation-leading commitment to early years literacy and numeracy,'' Victoria's minister, Martin Dixon, said.